Fabrication of hollow articles



Aug- 8, 1967 v. L.. MIDDLETQN FABRICATION OF HOLLOW ARTICLES 2 Sheets-Sheet l Filed Nov.

- mvENToR VfR/v5 L. M/ooLero/v BY? Jgd/W ATTORNEY Allg 8 1967 v. L. MIDDLa-:TQN 3,334,398

FABRICATION OF HOLLOW ARTICLES Filed Nov. 3, 1964 2 Sheets-Sheetl 2 I NVENTOR.

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A T TOR/VE Y United States Patent O 3,334,398 FABRICATION OF HOLLOW ARTICLES Verne L. Middleton, East Alton, Ill., assignor to Olin Mathieson Chemical Corporation, a corporation of Virginia Filed Nov. 2, 1964, Ser. No. 408,304 11 Claims. (Cl. 29-157.3)

This invention relates to the fabrication of hollow articles by expansion of sheet-like material and more particularly to a novel method of providing a pressure-tight seal around the pattern to be expanded, and to a novel blank to be employed in such a method.

This invention is directed primarily to the expansion of metal panels from blanks fabricated with an unjoined interior portion, but the invention is equally applicable to similar panels fabricated from materials other than metal, such as various plastics, and to panels fabricated from dissimilar materials such as metal and a plastic joined together with an unjoined portion between the sheets.

The hollow sheet-like material preferably in the form of sheet metal panels may be fabricated in accordance with various methods but are most advantageously and preferably made by a process such as described in U.S. Patent No. 2,690,002, issued to Grenell on Sept. 28, 1954, and known in the art as the Roll-Bond process.

In accordance with the process of the aforesaid patent to Grenell, a pattern of weld-inhibiting material is applied to a clean surface of a sheet of metal. A clean surface of a second sheet of metal is superimposed on this surface and the two sheets are secured to prevent relative movement between each other and then pressure-welded together, as by hot rolling, in their adjacent areas which are not separated by the weld-inhibiting material. Hot rolling of the sheets results in reducing the thickness of the two sheets and elongating the resultant blank in the direction of rolling while the width of the resultant blank remains substantially the same as the initial width of the sheets..

Following the pressure-welding operation, the resultant blank can be softened as by annealing to make it more.

pliable, and if desired, it may then be cold rolled to nal gauge and again softened as by annealing. The application of weld-inhibiting material results in an unjoined portion of a pattern of laminations between the outer faces of the pressure-Welded blank. Any time after pressure-welding of the blank, and preferably after softening by annealing, the unjoined portion or pattern of laminations is distended by injecting therein a fluid pressure of suflicient magnitude to permanently expand the blank in the area of the unjoined portion or pattern of laminations to form a desired corresponding system of passageways.

, Such a process may be employed to produce panels having expanded passageways on only one side or on both sides, as is now Well known in theart. This invention relates to the fabrication of panels` known in the art as one-side-at-that` is, having expanded passageways on only one side-or to those known as modied-one-sideflat-that is, those having expanded passageways on one side which are of a degree of expansion relatively minorV relative to the expansion of the passageways on the other side` l One conventional method of expanding a blank comprises subjecting the blank to external confinement between at least one rigid die member and a body of fluid, under pressure, applied externally to only one side of the blank. One of the rigid die members is in the form of a press platen with a suitably shaped die surface, such as a flat one in particular, on one side of the blank while a fluidpreferably compressed air, although a suitable incompressible liquid such as water, oil or the like may be employedacts on the other side of the blank so as to constrain it between the die surface and the fluid during the applica- Patented Aug. 8, 1967 tion of a blank-expanding fluid pressure injected internally of the blank into the unjoined portion or pattern of laminations. This fluid acting externally of the blank may be contained within a recess or cavity in a second rigid die member to act in conjunction therewith to control the height and the shape of the expanded portions of the blank. The recess, which is of a depth corresponding to the final height of the distension desired in the expanded portions of the blank, may be achieved either by providing a recess in the second die member or by spacing the blank above the second die member, as by a rubber seal.

Conventional apparatus for expanding such blanks thus comprises: An expansion press having a at movable platen and a stationary platen having a pan-like holding pressure cavity into which one side of a panel is to be expanded; a sealing ring encircling the operative portion of the cavity into which the panel expands; and a hydraulicv clampthe panel between the platens and thereby place oneV face of the panel in cavity-sealing engagement with the sealing ring and in position for expansion into the cavity; introducing a holding fluid into the cavity under pressure, say 1,000 p.s.i., to force the panel into face-to-face engagement -with the platen; introducing a hydraulic expansion fluid under pressure, say 3,000 p.s.i., into the unwelded passageway-forming system of said panel to expand the passageway walls of its lower face downwardly into the cavity; simultaneously releasing said hydraulic holding and expansion pressures; opening the press; and then removing the expanded panel.

When employing the above method, several problems are encountered. First, the dies and seals employed are necessarily of various sizes according to panel requirements; it is not economically feasible to employ a universal die or a universal sealing member. Loading and unloading of the various dies cause damage to the presses and require considerable set-up time. Furthermore, the conventional rubber seals are subject to rupture under pressure. Considerable production time is consequently lost in replacing damaged rubber seals.

. The present invention comprehends complete elimina- Y tion of the standard rubber seal, or at least a major reduction in the extent of seal employed, by initial inflation of a peripheral tube of the blank. Conta-ct of the tube with a restraining means provides the pressure seal here,- tofore achieved by use of particular dies and rubber sealing rings or the like.

By the use of the present method and a novel blank it is possible to use optimum plate sizes on all parts toV It is a further object of Ithis invention to produce such hollow articles without the use of standard rubber seals. `It is la still further object of this invention to provide an improved method for fabricating hollow articles.

.,lIt is a still further object of this invention to provide a novel blank to be employed in Ithe improved methodV of fabricating hollow articles.

Additional objects and ladvantages will become apparent 'from .the following description and drawings in which:

FIGURE 1 is a perspective view of a sheet of metal having a pattern of weld-inhibiting material applied to a surface thereof.

` j FIGURE 2 is a schematic perspective view of the` sheet as shown in FIGURE 1 having superimposed thereon a second sheet of meta-l with the pattern of weldinhibiting material sandwiched between the sheets and showing the sheets being welded together while passed through a pair of mill rolls.

FIGURE 3 is a Icross-sectional view through one form of blank to be employed in the instant invention, showing the sheet having the pattern of weld-inhibiting material.

FIGURE 4 is a View simil-ar to FIGURE 3 showing a second form of blank, with a portion of the superimposed sheet shown in place.

lFIGURE is a sectional view showing the blank of this invention in a first step of production.

FIGURE 6 is a View similar to FIGURE 5 showing a second step of production.

Referring to the drawings, FIGURES 1 and 2 illustrate t-he fabrication of blanks by the Roll-Bond process. FIG- URE 1 illustrates a sheet of metal 1 having applied to a clean surface 2 thereof a pattern of weld-inhibiting material 3. FIGURE 2 shows the sheet 1 having superimposed thereon a second sheet 4 with the pattern of weld-inhibiting material 3 sandwiched between the sheets. The sheets 1 and 4 are tacked together as by spot-welds 5 to prevent relative slippage between the sheets as they are subsequently welded together by passing through a pai-r of mill rolls 6 to form a blank 7. It is normally necessary that the sheets 1 and 4 be heated prior to passing through the mill rolls to assure lthat they weld to each other in keeping with techniques well known in the rolling art. The sheets 1 and 4 are separated by ythe weld-inhibiting pattern 3 resulting in an Aunjoined portion as for example the pattern shown in FIGURE l.

Referring now to FIGURES 3 and 4, there are shown the particular blanks to be employed in the instant method. Referring first to FIGURE 3 a first form of blank is shown comprising a sheet of metal 8 having applied Ithereon a pattern 9 of weld-inhibiting material. The pattern comprises an inlet 10 extending from an outer edge 11 of the sheet 48 and in a path 12 around the periphery of the sheet 8. Within the pat-tern 12 is a second pat-tern 1'3 joined Aat one end to the first pattern 12 as at 14, but spaced from the pattern 12 at its opposite end 14. The patern 13 may take any form according to its intende-d use and customer specifications. At or near the jointure 14 is a restrictor portion 15. This restrictor portion is formed 4when the blank is assembled from the sheets 1 and 4; when lthe pattern of weld-inhibiting material 9 is applied to the sheet 1 a stencil pattern is employed in order to form a reduced portion in the weldinhibiting material. This narrowed portion is pre-calculated to provide Ithe pressure-restricting function, to be discussed hereinafter. It will be evident that a second sheet is to be superimposed on the sheet 8, in the manner indicated hereinbefore.

Referring now to FIGURE 4, ya second form of blank is shown comprising la sheet 16 having thereon a firs-t pattern 17 and a second pattern 18 of weld-inhibiting material. The first pattern 17 extends around the periphery `of the sheet 16 and encompasses the pattern 1'8- which, like the pattern 113' of FIGURE 3, may take any desired configuration. Each of the patterns 17 and 18 extend from an outer edge of the sheet 16, as at 19 and 20 respectively, about the blank, and thence returning to an outer edge as at 21 and 22. A second sheet, a portion of which is shown at the upper portion of FIG- URE 4, is superimposed on the sheet 16 in the manner indicated hereinbefore. For reasons to be indicated shortly, a rubber seal 23 is placed on the completed blank across the patterns 17 and 18 near the terminal portions thereof.

In FIGURES 5 and 6 is shown the subsequent inflation of either of the blanks of this invention. As the inflation of the second embodiment las depicted in FIGURES 5 and 6 is identical to that for the first embodiment, only the latter will be described, it being understood that 4, references -to the blank 8, the first pattern 12, and the second pattern 13 are equally applicable to their analogous struct-ure blank 16, first pattern 17, and second pattern 18, respectively.

The blank 8 is first placed on the flat surface of a first platen 24 of a suitable press. The second platen 25 is next lowered to a height corresponding to the desired distension of the finished hollow article. The first pattern 12 is then expanded by suitable application of internal pres-sure in the well-known manner. This pressure is of a degree higher than the subsequently-applied holding pressure, for reasons to be noted. The second pattern 13 remains unexpanded. In the case of the blank of FIGURE 3, the internal pressure is introduced through the inlet 10 and thence into the pattern 12. The pattern 13 will not inflate at the initial introduction of pressure as such pressure is below that required to crack the restrictor portion 15. In the case of the blank of FIGURE 4, the internal pressure is introduced at 19 and only the pattern 17 infiates, as the patterns 17 and 18 are not in communication in this embodiment.

Proper inflation of the pattern 12 into flush engagement with the platen 25 provides a pressure-tight yseal for the volume between the blank 8 and the platen 25, this volume being designated generally as 26. Pressure is introduced into the volume 26, in a manner obvious to those skilled in the art, for instance, through conduit means 37, which may be termed the holding pressure, and thus secures the blank 8 to the platen 24 andby proper regulation in the Iwell-known mannercontrols the subsequent distension of the pattern 13. For example, a modifiedone-side-flat may be produced by appropriately lowering the holding pressure, which allows a controlled amount of distension on the face of the blank in contact with the platen 24. In the instant invention, a higher holding pressure is possible than in the prior art devices, for the reason that the internal pressure inflating the pattern 12 may be materially higher than the holding pressure and hence provide a more positive seal unattainable by the prior art rubber seals.

The subsequent distension is shown in FIGURE 6, wherein the pattern 13 has been inflated by application of suitable distending internal pressure. In the case of the blank of FIGURE 3, the restrictor portion 15 cracks at the design pressure, and the pressure introduced at 10 extends through the pattern 13. The pressure required to crack the restrictor portion is contingent upon its crosssectional area, which is calculated commensurate with the proper decompression rate. For example, for a pressure within the pattern 12 of 2,600 p.s.i. and a holding pressure of 850 p.s.i., the restrictor portion 15 may be designed so as to crack within the range of L200-1,800 p.s.i.

In the case of the blank of FIGURE 4, a control valve at 27 seals the inflated pattern 17, which is closed off at its opposite end 22, and automatically control valve 28 introduces inflation pressure to pattern 18, which is closed off at its opposite end 21. In the embodiment of FIGURE 4, the peripheral pattern 17 does not extend entirely around the pattern 18, and hence it is necessary to provide a short rubber seal 23 to provide the required seal at the area where pattern 17 does not encompass pattern 18.

Following inflation of the pattern 12, the entire system may be decompressed. The inflated blank of FIGURE 3 will decompress through restrictor tube 15 and inlet 10 to atmosphere, and the blank of FIGURE 4 through control valves 27, 28. The inflated blank is removed, the pattern 12 is cut oil and discarded, and the resulting blank with pattern 13 may be further processed commensurate with its intended use.

Although the invention has been described with reference to particular embodiments, materials, and details, various modifications and changes will be apparent to one skilled in the art, and the invention is therefore not to be limited to such embodiments, materials or details eX- cept as set forth in the appended claims.

What is claimed is:

1. A method of distending a blank formed of superimposed sheets having selected portions of their adjacent surfaces joined together to define between said sheets a formation of internally unjoined areas corresponding to a desired configuration with said areas comprising a first unjoined area and a second unjoined area, said method comprising:

(A) positioning the blank on a first restraining means,

(B) applying distending fluid pressure into said first unjoined area to distend said first unjoined area into pressure-tight relationship with a second restraining means,

(C) applying holding pressure into the volume between said blank and said Isecond restraining means, and

(D) applying distending uid pressure into said second unjoined area, to distend said second unjoined area, distension being greater on the side adjacent said second restraining means than on the side of said blank adjacent said first restraining means.

2. A method according to claim 1 in which there is substantially no distension on the side adjacent said first restraining means.

3. A method according to claim 1 in which said first restraining means is a first platen and said second restraining means is a second platen.

4. A process according to claim 1 in which the fluid pressure applied to said second unjoined area is applied through an unjoined area connecting said first unjoined area with said second unjoined area.

5. A process according to claim 4 in which the cross sectional area of the unjoined area connecting said first unjoined area with Said second unjoined area is smaller at least in part than the cross sectional area of either said first unjoined area or said second unjoined area.

6. A process according to claim 1 wherein said second unjoined area extends to the surface of said blank and the pressure applied to said second unjoined area is applied through a connection at the extension of said second unjoined area to said surface.

7. A method of distending a blank formed of superimposed sheets having selected portions of their adjacent surfaces joined together to define between said sheets a formation of internally unjoined areas corresponding to a desired configuration with said areas comprising a irst unjoined area and a second unjoined area, with said first unjoined area being in communication with said second unjoined area, said method comprising:

(A) positioning the blank on a first restraining means,

(B) applying a first distending Huid pressure into said first unjoined area to distend said first unjoined area into pressure-tight relationship with a second restraining means, said rst pressure being insutiicient to distend said second unjoined area,

(C) applying holding pressure into the volume between :said blank and said second restraining means to clamp said blank on said first restraining means and to regulate the subsequent distension of said second unjoined area, and

(D) applying a second distending fluid pressure into said second unjoined area, said second pressure being greater than said first pressure and being sufficient to expand said second unjoined area, the expansion being greater on the side of said blank adjacent said second restraining means than on the side of said blank adjacent said tirst restraining means.

8. The method of `claim 7 wherein said first and second unjoined areas are in communication through an area which at least in part has a reduced cross section.

9. A blank for producing an article having a desired Syste-m of internal tubular hollows, comprising:

(A) a first sheet and a second sheet, said sheets being in superimposed relationship,

(B) a first continuous pattern of stop-weld material disposed on at least one of said sheets and in the yconfiguration of said desired system of internal tubular hollows,

(C) a second continuous pattern of stop-weld material disposed on at least one of said sheets and substantially surrounding said first pattern,

(D) said first and second sheets being secured together in substantially all the portions of said sheets not occupied by stop-weld,

(E) said first and second patterns being joined by a yportion of stop-weld material, at least a part of which joining portion has a section of restricted cross sectional area to allow distension of said second pattern while not permitting expansion of said first pattern until a pressure greater than that required to distend said second portion is reached.

10. The blank of claim 9 wherein said second pattern completely surrounds said first pattern.

11. The blank of claim 9 wherein said first and second patterns each have end portions terminating at an edge of one of said sheets.

References Cited UNITED STATES PATENTS 2,896,312 7/1959 Schnell 29-157.3 2,920,377 1/1960 JanOs.

2,948,053 8/ 1960 Goff 29--157.3 2,991,047 7/ 1961 Bailys.

3,038,246 6/1962 VanCamp et al 29-157.3 3,140,755 7/1964 Tranel.

3,170,229 2/1965 Wengler 29-157.3

JOHN F. CAMPBELL, Primary Examiner. J. D. HOBART, I. L. CLINE, Assistant Examiners. 

1. A METHOD OF DISTENDING A BLANK FORMED OF SUPERIMPOSED SHEETS HAVING SELECTED PORTIONS OF THEIR ADJACENT SURFACES JOINED TOGETHER TO DEFINE BETWEEN SAID SHEETS A FORMATION OF INTERNALLY UNJOINED AREAS CORRESPONDING TO A DESIRED CONFIGURATION WITH SAID AREAS COMPRISING A FIRST UNJOINED AREA AND A SECOND UNJOINED AREA, SAID METHOD COMPRISING: (A) POSITIONING THE BLANK ON A FIRST RESTRAINING MEANS, (B) APPLYING DISTENDING FLUID PRESSURE INTO SAID FIRST UNJOINED AREA A DISTEND SAID FIRST UNJOINED AREA INTO PRESSURE-TIGHT RELATIONSHIP WITH A SECOND RESTRAINING MEANS, (C) APPLYING HOLDING PRESSURE INTO THE VOLUME BETWEEN SAID BLANK AND SAID SECOND RESTRAINING MEANS, AND (D) APPLYING DISTENDING FLUID PRESSURE INTO SAID SECOND UNJOINED AREA, TO DISTEND SAID SECOND UNJOINED AREA, DISTENSION BEING GREATER ON THE SIDE ADJACENT SAID SECOND RESTRAINING MEANS THAN ON THE SIDE OF SAID BLANK ADJACENT SAID FIRST RESTRAINING MEANS.
 9. A BLANK FOR PRODUCING AN ARTICLE HAVING A DESIRED SYSTEM OF INTERNAL TUBULAR HOLLOWS, COMPRISING: (A) A FIRST SHEET AND A SECOND SHEET, SAID SHEETS BEING IN SUPERIMPOSED RELATIONSHIP, (B) A FIRST CONTINUOUS PATTERN OF STOP-WELD MATERIAL DISPOSED ON AT LEAST ONE OF SAID SHEETS AND IN THE CONFIGURATION OF SAID DESIRED SYSTEM OF INTERNAL TUBULAR HOLLOWS, (C) A SECOND CONTINUOUS PATTERN OF STOP-WELD MATERIAL DISPOSED ON AT LEAST ONE OF SAID SHEETS AND SUBSTANTIALLY SURROUNDING SAID FIRST PATTERN, (D) SAID FIRST AND SECOND SHEETS BEING SECURED TOGETHER IN SUBSTANTIALLY ALL THE PORTIONS OF SAID SHEETS NOT OCCUPIED BY STOP-WELD, (E) SAID FIRST AND SECOND PATTERNS BEING JOINED BY A PORTION OF STOP-WELD MATERIAL, AT LEAST A PART OF WHICH JOINING PORTION HAS A SECTION OF RESTRICTED CROSS SECTIONAL AREA TO ALLOW DISTENSION OF SAID SECOND PATTERN WHILE NOT PERMITTING EXPANSION OF SAID FIRST PATTERN UNTIL A PRESSURE GREATER THAN THAT REQUIRED TO DISTEND SAID SECOND PORTION IS REACHED. 